The most critical junction in a heterojunction bipolar transistor is the interface between the base and emitter layers. In previous epitaxial overgrowth heterojunction bipolar transistor fabrication processes, the interface between the initial epitaxial layers and the emitter overgrowth layers occurs at the base-emitter junction of the heterojunction bipolar transistor. In such a process, the base layer is exposed to various processes prior to the emitter overgrowth process. Through this exposure, the base layer may be damaged or washed away by various fabrication process steps. A poor overgrowth interface can result in large numbers of interface states resulting in poor current gains due to recombination in the base-emitter junction. Therefore, it is desirable to fabricate a heterojunction bipolar transistor that avoids exposing the base layer or the base-emitter interface to unnecessary fabrication process steps.